1. Field of the Invention
The present invention relates to a device and method for using a stable chlorine dioxide solution in bioeradication processes such as sterilization, disinfection, and sanitation in various food, agricultural, hospital and medical industries. More specifically, the invention pertains to stabilizing a biocide agent in an atomized mist phase solvent to create a homogeneous gas-like mist for fumigation and sterilization of surfaces and volumes of all scales.
2. Description of Prior Art
A tremendous urge for the present invention comes from the November 2001 instances of anthrax decontamination of federal buildings and continued future threats of bioterrorism. Some specific instances involve anthrax delivered in sealed envelopes. Surprisingly, anthrax was found airborne, on surfaces and in contained volume spaces, such as sealed packages. Anthrax spores are on the order of 1-5 microns, which in turn can diffuse under favorable conditions of paper porosity, physical structure and time of exposure, pressure, temperature and flow conditions.
Based on the immediate necessity to decontaminate large volumes of the Hart Senate Building, the government used gaseous chlorine dioxide as a biocide. However, prior to this use of chlorine dioxide for such large volumes, the stability, toxicity and effectiveness of the chlorine dioxide gas for such application remained undetermined. Besides other problems, the chemical instability of chlorine dioxide gas in concentrations exceeding 1000 ppm in gas phase resulted in poor decontamination efficiency. In order to increase the effectiveness of chlorine dioxide gas in decontamination, steam was flushed into the treatment area to increase the humidity and help stabilize the chlorine dioxide gas.
Chlorine dioxide has attracted considerable attention for its use in sterilization, disinfection, and sanitation due its superior properties. In particular, chlorine dioxide is relatively less toxic in a solution with water compared to free chlorine and bleach solutions. Chlorine dioxide does not react to form other chemicals when dissolved in water, an attractive advantage compared to other chlorine containing bleaching agents. However, chlorine dioxide is not very stable as a gas, making its use in gaseous state as a biocide and its storage and transportation very problematic.
Hence, because of the chemical instability of chlorine dioxide gas at relatively high concentrations, its use as a disinfectant/sanitizer is less common compared to its use in solution form. Gaseous chlorine dioxide as a disinfectant for surfaces and implements is disclosed in U.S. Pat. Nos. 4,908,188, 4,681,739 and 4,504,442 and has been studied for application in the food processing and poultry industries. All of these prior attempts to stabilize and apply chlorine dioxide gas have found that better disinfection is obtained at very high humidity levels (80%), indicating the need to stabilize the chlorine dioxide gas using moisture or humidity similar to the outcome in the Hart Senate building case in which steam was injected into the building.
U.S. Pat. No. 5,989,497 to Roland R. Labonte, Jr. proposes using a mist of chlorine dioxide solution generated by high-pressure atomization to deodorize malodorous substances. However, Labonte does not discuss recently discovered issues concerning the separation of chlorine dioxide from the solution during atomization and the resulting instability of the separated chlorine dioxide biocide agent. Electrostatic, high-pressure, or ultrasonic atomization leads to gas separation of the chlorine dioxide from the liquid solution. Ambient pressure ultrasonic atomization is the most attractive way of generating a mist solution of biocide without using pressure or electric charge or heat, but the mechanics of the ultrasonic wave propagation still causes the chlorine dioxide to distill as gas. The distilled gas escapes as the unstable chlorine dioxide gas substance, prior to the atomization of the water inside the mist generator. When Chlorine dioxide solution is atomized using widely used methods such as electrostatic and pressure atomization technologies, the gas separates from the solution, leaving behind water or the solvent. As such, these methods cannot be effectively utilized to produce aqueous chlorine dioxide mist. Moreover, pressure atomization of chlorine dioxide solution is not safe and can be explosive at high enough concentration.
Thus, Labonte does not provide a complete solution to the stabilization problem and a continuing need exists for obtaining a stable mist of chlorine dioxide dissolved in a solvent such as water that is highly effective in sterilization and the like. Because chlorine dioxide decomposition is primarily responsible for the substance's power in oxidizing organic matter, microorganisms, bacteria, and bacterial spores, a need exists to provide chlorine dioxide in a stable form in which the chlorine dioxide will not rapidly decompose prior to it interacting with the desired treatment site. A gas phase or pseudo-gas phase means for providing and using stable chlorine dioxide is needed to provide a mobile chlorine dioxide solution efficient in the treatment of rooms and buildings or smaller-scale applications. Such a means for applying chlorine dioxide as a biocide agent should avoid using potentially damaging levels of humidity or temperature or dangerous high-pressure delivery systems.